Conventionally, a driving method called “CC (Charge Coupling) driving” is used in an active matrix liquid crystal display device. The CC driving is disclosed, for example, in Patent Literature 1. The following describes the CC driving with reference to descriptions disclosed in Patent Literature 1.
FIG. 24 is an equivalent circuit diagram illustrating a structure of a device for carrying out the CC driving. FIG. 25 is a timing chart illustrating operating waveforms of various signals in the CC driving.
As shown by the equivalent circuit illustrated in FIG. 24, a liquid crystal display device which carries out the CC driving includes an image display section 110 which includes: a plurality of source lines (signal lines) 101; a plurality of gate lines (scan lines) 102 which intersect with the plurality of source lines 101 at right angles; switching elements 103 respectively provided near to each of the intersections; pixel electrodes 104 respectively connected to the switching elements 103; a plurality of CS (Capacity Storage) bus lines (common electrode lines) 105 which are respectively paired with the plurality of gate lines 102, and are aligned in parallel with each of the plurality of gate lines 102; storage capacitors 106 provided between the pixel electrodes 104 and the plurality of CS bus lines 105; a counter electrode 109; and a liquid crystal 107 provided between the pixel electrode 104 and the common electrode 109.
Each switching element 103 is formed from amorphous silicon (a-Si), polycrystalline polysilicon (p-Si), monocrystalline silicon (c-Si), or the like. Further, the switching element 103 has a structure in which a capacitor 108 is formed between a gate and a drain. Due to the capacitor 108, a phenomenon is occurred in which an electric potential of the pixel electrode 104 is shifted to a negative side by a gate pulse supplied via the gate line 102.
Further, the liquid crystal display device includes, outside of the image display section 110: a source line driving circuit 111 (source driver) which drives the source lines 101; a gate line driving circuit 112 (gate driver) which drives the gate lines 102; and a CS driving circuit 113 (CS driving circuit) which drives the CS bus line 105.
FIG. 25 shows operating waveforms of various signals in the liquid crystal display device. A waveform Wg of a gate line 102 is at a voltage Von only during an H-period (horizontal scan period) during which the gate line 102 is being selected. During the other periods, the waveform Wg maintains at a voltage Voff. A waveform Ws of a source line 101 is inverted in polarity in every H-period and, on an identical gate line 102, polarities are alternated in every H-period (line inversion driving). Note that, the polarities are inverted with amplitude which differs in accordance with a signal of video to be displayed. However, in FIG. 25, amplitude of the waveform Ws is constant based on the assumption that a uniform video signal is supplied.
In the period during which the waveform Wg is being at the voltage Von, the switching element 103 is being conductive, whereby a waveform Wd of the pixel electrode 104 has a same electric potential as that of the waveform Ws of the source line 101 during the period. Whereas, when the waveform Wg is turned to be at the voltage Voff, a voltage of the waveform Wd is slightly shifted to the negative side due to the capacitor 108 between the gate and the drain.
A waveform We of the CS bus line 105 is at a voltage Ve+ during (i) an H-period during which a corresponding gate line 102 is being selected and (ii) the next H-period. In a H-period after the next, the voltage Ve+ is switched to Ve−, and then the voltage Ve− is maintained until a next field. The switch of the voltage shifts a voltage of the waveform Wd of the pixel electrode 104 to the negative side due to the storage capacitor 106.
As a result, the waveform Wd of the pixel electrode 104 obtains large amplitude than that of the waveform Ws of the source line 101. This allows the waveform Ws of the source line 101 to have smaller amplitude. The configuration gives the source line driving circuit 111 a simplified circuit structure and reduced power consumption.
Patent Literature 1
    Japanese Patent Application Publication, Tokukai, No. 2001-83943 A (Publication Date: Mar. 30, 2001)